Broad objective of work is to effect significant improvements in aerosol therapy through increased understanding and control of the growth and evaporation processes of therapeutic aerosols in the respiratory system. Specifically, the work includes experimental investigation of growth rates of existing medical aerosols ranging in mean size from 0.03 to 30 um, development of a model for therapeutic particle growth and deposition in the respiratory system, and investigation of nontoxic surface active and encapsulating agents to control particle growth.